Position reporting devices are frequently used to locate and report the position of a person or object. A typical position reporting device combines a navigation system such as the Global Positioning System (GPS) module with a mobile communications system such as a cellular modem to determine the position or geographic location of a person or asset being tracked and report their position to a tracking facility. Position reporting devices are used in a variety of systems in which timely position information is required such as fleet tracking and asset recovery systems.
Fleet tracking systems allow a user to monitor the position of a ship or vehicle carrying a position reporting device by sending a succession of position fixes. The phrase “position fix” refers to a process of determining an unknown location using a fixed reference point or points. For example, the course of a vehicle being tracked can be inferred using successive position fixes sent by the position reporting device. In a similar manner, it can be inferred that the vehicle is not moving when successive position fixes report the same position. Fleet tracking systems are commonly used by delivery services for routing and dispatching of vehicles. Asset recovery systems report the position of stolen or missing property (e.g., a stolen car) to a service provider or to the police in order to facilitate recovering the property.
A drawback associated with position reporting devices is the amount of power they consume. While battery powered position reporting devices do exist, the amount of power they consume when turned on can necessitate frequent battery changes in order to continue operating. This makes using position reporting devices inconvenient to some users in that they can require an excessive amount of maintenance to continue operating.
Recently, concerns have been communicated regarding the operation of various electronic devices in certain environments. For example, airlines request that passengers refrain from using mobile telephones and laptop computers during takeoffs and landings because they can cause electromagnetic interference that can impair the operation of navigational and other instrumentation systems aboard airplanes. Since July of 2001, the Pentagon has had a moratorium on the construction of additional wireless communications networks, and bars connections to classified networks or computers using devices that are not explicitly approved by the Department of Defense. This is to prevent the unintentional compromise of secure data and includes personal wireless devices such as pagers, Personal Data Assistants (PDAs), and wireless electronic mail (e-mail) devices. As another example, many public facilities such as theaters and restaurants now request that their patrons turn off their wireless devices (e.g., mobile telephones and pagers) while on their premises.